Abstract: A self-tensioning device for snow chains (2) for vehicles includes an outer element (3) closable in a ring, suitable to be placed on the outer side of the wheel (1), an inner element closable in a ring, suitable to be placed on the inner side of the wheel (1), inner and outer elements being joined by variously composed elements (10) creating the traction on the tread, the outer element having a terminal portion (7) passing through a non-return device (5) which makes it slide only in the chain tensioning direction and not in the opposite slackening direction, a storage block (20) containing an elastic element (21) able to hook, tension and retain the terminal portion (7) being provided on the outer ring.